The statements in this section merely provide background information related to this disclosure and do not necessarily constitute prior art.
Electrically conductive elastomers (ECEs) may be made into electromagnetic interference (EMI) blocking or mitigating gaskets of indeterminate length or circumference. Many such gaskets may have a round cross-sectional profile. Compression forces imposed upon these round profile gaskets when in use may result in imperfect performance such that the compression of the gasket may be non-uniform through the length of the gasket. Additionally, when these round profile gaskets are manufactured into a continuous circumference, the gasket is first extruded and then fused at opposing ends to create a continuous looped gasket, leading to a more costly and error-prone product. Finally, these round profile gaskets have sub-optimal performance around ninety degree corners, leading to possible penetration of electromagnetic interference and an incongruent seal.
Round profile EMI gaskets 100 of the prior art, as seen in FIGS. 1A, 1B, 1C, 2A, and 2B, have several disadvantages. Due to their shape, compression forces placed on the gasket when installed on a metal EMI cage 102 result in inconsistent compression and deflection, as well as undesirable forces required to compress the gasket into a suitable EMI shield. When a non-watertight seal is required, additional compression forces needed to compress the gasket and complete the EMI seal are undesirable. It should be noted that the particular example of a metal EMI cage 102 as seen in FIG. 2B is not necessarily prior art.
A round profile gasket 100 as shown in FIGS. 1A-1C, when installed on a metal EMI cage 102 as seen in FIG. 2B, may compress as seen in FIG. 2A. A round gasket with a diameter of 2.62 millimeters (mm), for example, when installed in an opening of 2.62 mm×2.30 mm, has an actual installed height of 2.84 mm. When compressed to a height of 1.82 mm, in this example, the gasket required a force of 0.62 Newtons per millimeter (N/mm). But due to the compression forces when installed, the round face gasket would bulge out beyond the tabs 104 of the metal EMI cage in FIG. 2B, creating additional forces on the gasket and cage. These forces, determined by finite element analysis, included a deformation force of 4.4 N over a 7.125 mm segment near the bulge around the tabs.